A head-up display (HUD) apparatus provides imagery for a viewer, typically a simulator trainee or an operator of a vehicle, such as an airplane, a ground vehicle, a boat, or other moving vehicle, with imagery that includes certain information that may be useful in the context of the scene perceived by the viewer. For example, in the context of a car, a HUD apparatus may display the current speed of the vehicle and the current speed limit of the road on which the vehicle is located.
Domed simulators are often used to train pilots. Typically the HUD imagery is provided via a rear projector that displays the imagery on the dome for viewing by the trainee inside the dome. One problem with this approach is that the imagery can be seen even when not looking through the HUD apparatus, which generates negative training in the sense that the trainee does not become conditioned to looking through the HUD apparatus to see the HUD imagery.
Actual HUD apparatuses used in an aircraft are prohibitively expensive for use in a simulator. Also, an actual HUD apparatus focuses the HUD imagery at infinity, which would be undesirable in a simulator, and expensive modifications would be required to modify the HUD apparatus for use in a domed simulator.
In a domed simulator it would be preferable to focus the HUD imagery on the dome to reduce eyestrain of the trainee who would otherwise need to continually refocus her eyes as she alternates between the out-the-window scene which is focused on the dome and the HUD imagery focused at infinity.